Table 4.

Performance of commonly theoretical methods for the energetics (mean absolute errors in kcal mol⁻¹) of bond separation reactions.^a

Reaction Classb	HF/cc-pVTZ	B3LYP/6-31G(d)	M05-2X/6-31G(d)	M06/6-31G(d)	M06-2X/6-31G(d)	MP2/cc-pVTZ	CCSD(T)/cc-pVTZ
Conjugated hydrocarbons (Set A)
RC0	327.93	7.03	8.88	2.09	1.96	6.15	35.10
RC1	21.08	9.87	21.53	10.27	10.51	1.91	2.93
RC2	3.96	7.06	3.71	8.31	4.47	3.59	0.31
RC3	1.77	1.75	0.91	1.25	0.98	1.41	0.55
RC4	0.29	0.24	0.24	0.40	0.22	0.49	0.17
RC5	0.18	0.11	0.18	0.32	0.19	0.43	0.14
Non-conjugated hydrocarbons (Set B)
RC0	356.89	10.62	9.75	3.84	3.18	12.12	37.00
RC1	20.34	13.02	16.93	9.83	8.06	0.94	2.85
RC2	3.92	2.67	1.18	2.51	1.30	1.88	0.16
RC3 = RC4	0.67	0.38	0.21	0.34	0.18	0.40	0.19
RC5	0.14	0.14	0.18	0.28	0.21	0.22	0.19
Cyclopentadiene and 1,3-cyclohexadiene (Set C)
RC0	321.94	10.72	6.36	3.32	2.17	3.29	34.97
RC1	24.20	13.51	18.94	12.37	10.69	0.34	3.71
RC2	6.07	0.14	0.19	1.56	0.58	3.74	0.59
RC3	0.46	0.37	0.70	1.16	1.40	1.48	0.13
RC4	0.41	1.45	1.26	1.92	1.82	0.90	0.15
RC5	0.85	1.15	1.44	2.09	2.16	0.75	0.35

^aErrors relative to FPA benchmarks in Table 3. All energies were evaluated at B3LYP/6-31G(d) optimized geometries. Details for each reaction are provided in Supporting Information.

^bAbbreviations: RC0 = atomization, RC1 = isogyric, RC2 = isodesmic, RC3 = hypohomodesmotic, RC4 = homodesmotic, RC5 = hyperhomodesmotic.